This invention relates generally to lamp assemblies and more particularly to lamp assemblies comprising molded plastic housings and molded plastic lenses.
Presently the plastic housings and the plastic lenses are molded in separate molding machines. The molded plastic housings and the molded plastic lenses are then assembled in another machine and secured to each other by various methods. Assembling the molded plastic housings and the molded plastic lenses in a separate machine for securing the housings and lenses together is costly from a manufacturing standpoint because the parts are handled several times. Moreover, this method introduces inaccuracies in the alignment of the lenses and the housings because of dimensional variations between the molding dies and the fixtures of assembly machine.
It is also known that hollow parts can be molded without cores in a die slide injection molding method (DSI) in which two separate halves of the hollow part are injection molded of the same material simultaneously in the same machine. The molded halves are then assembled together in this same machine by realigning the die set and injecting the same material to secure the halves of the part to each other. In this known DSI method, each die has a male and a female mold cavity in a linear arrangement. One die is mounted on a moveable platen of the molding machine and the mating die is mounted on the fixed platen. The mating die mounted on the fixed platen includes a slide for realigning the dies for assembly of the separate molded halves of the hollow part. The die set is opened after the separate halves are injection molded and the slide is then actuated to realign the dies so that the female mold cavities containing the molded halves are mated. The realigned dies are then closed and the molded halves are secured to each other by a secondary injection of the same material into the mated female cavities.
This DSI molding method claims to have cost advantages in producing hollow parts. However, this known DSI molding method is not suitable for manufacturing lamp assemblies. For instance, the known DSI method molds two identical halves of the same material and then attaches the two identical halves together with this same material. On the other hand, lamp assemblies require housings and lenses of different colors and preferably of different materials specifically suited to the individual needs of each component. Moreover, the DSI molding method requires expensive tooling because the die set includes a slide for realigning the die set to assemble the molded halves of the part. Because of this slide, the DSI molding method is also not well suited for accurate assembly of components such as required by a lamp assembly comprising housing and lens because accurate alignment must be built into each die set rather than simply relying on the accuracy of the molding machine. The placement of the slide on the fixed platen also requires multiple feed passages through the slide even though the same plastic material is used to mold the two halves of the hollow part and to secure the molded halves together.